Picked up half a megawatt worth of Caterpillar power, think I'll make a PTO generator

strantor · Oct 22, 2018

I guess this will be a build thread.

Living in hurricane country for the past few years with nothing but a 3,500W harbor freight generator that never works when I need it, I've been wanting a whole-home generator and been keeping my eye out for a used one. They don't come up for sale used; I guess people only get rid of them when they quit working. So I thought I'd get a PTO generator, and found they ain't cheap either. So then I thought I'd build one. Been eyeballing these ST generator heads on eBay for a while, finally set aside some funds to get one, log into eBay and I find a local guy liquidating an Oil field Caterpillar generator shop.

He's got 300kW generator heads for sale, half the price of a 30kW eBay ST head. So before you ask "WHY do you need a generator that big?" - I don't. I got an unbelievable deal.

I came home today with a pair of 210kW Caterpillar SR4B generator heads and together they cost less than the reasonably sized one I set out to buy.

That's all I accomplished today. Got the generator heads home. Next I'll have to figure out how to put a bearing on the end and some kind of cover and gearbox with a PTO interface. I'm thinking a truck rear end with welded gears, ran in reverse (PTO power to axle, pumpkin output to generator) to step up the speed from 540RPM to 1800RPM. Something with a gear ratio as close as possible to 3.33.

One of them appears refurbished, and unused since refurb, however the enclosure has been badly bent. The other one is obviously used and has a shorted stator (despite claims it came off a working generator) but whatever, it was dirt cheap and I'll probably just keep it for spare parts. I want to incorporate a load cell into it somehow So it can serve double duty as a PTO dynomometer.

1010 · Oct 22, 2018

They make large leaver type clutches just for this type thing. Real common on irrigation motors that are able to move around.

EDIT:
But the one I'm thinking about is bolted directly on the back of an engine. I see some well heads with gas V-8 engines turning them. And a drive shaft coming from the clutch to the pump head.

I have seen some straight six engines on a few pumps also. PROPANE! I'd bet a pump place can gear a clutch to what you'd need. And not have a lot of money tired up.. It'd be reliable too.

strantor · Oct 22, 2018

1010 said:
They make large leaver type clutches just for this type thing. Real common on irrigation motors that are able to move around.

EDIT:
But the one I'm thinking about is bolted directly on the back of an engine. I see some well heads with gas V-8 engines turning them. And a drive shaft coming from the clutch to the pump head.

I have seen some straight six engines on a few pumps also. PROPANE! I'd bet a pump place can gear a clutch to what you'd need. And not have a lot of money tired up.. It'd be reliable too.

I don't follow. These generators are meant to bolt directly to an engine. They have a bearing on one end only. The other end is meant to be supported by the crankshaft. The large round disk is meant to bolt to the flywheel I believe. Are we talking about the same thing? If so, please expound because I can't picture anything remotely similar to what you are describing.

1010 · Oct 23, 2018

The above clutch would bolt on the engine.

The existing plate that's on the unit would have to replaced or retrofitted to accept the shaft from the clutch.

Snobdds · Oct 23, 2018

Yea this is common in irrigation, especially center pivot wells. A big generator runs the pump and pivot.

What engine are you going to power that? I've seen Ford industrial straight 6 motors going 30,000 hours on generator duty.

strantor · Oct 23, 2018

1010 said:
View attachment 575829
The above clutch would bolt on the engine.

The existing plate that's on the unit would have to replaced or retrofitted to accept the shaft from the clutch.

Ok I get it now, but I think there's been a misunderstanding. I'm going to try to couple the generator to my tractor's PTO, not to an engine. At least not yet. I have a propane forklift engine I might couple the 2nd generator to if I can get both generators working, but for now the plan is get one working generator coupled to the tractor PTO.

BUT... your idea does give me an idea. Instead of bolting that clutch bellhousing to an engine, maybe I could bolt it to the generator head. Use the flywheel adapter to bolt to the generator's flex plate, and now I have a keyed shaft stub sticking out and the rotor is now supported by 2 bearings. I would just leave the clutch engaged at all times.

herm0016 · Oct 23, 2018

1 hp = 745 watts

210 kw = 283 hp

your ls has 32 pto hp??

these heads may be 460 volt 3 phase? seems like a large problem to get this to work on your tractor....

you may not even have enough HP to excite the winding.

looks like the sr4b is usually paired with a ~500 hp 3456 ....